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73 lines
2.4 KiB
Markdown
73 lines
2.4 KiB
Markdown
# package-hash
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Generates a hash for an installed npm package, useful for salting caches.
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[AVA](https://github.com/sindresorhus/ava) for example caches precompiled test
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files. It generates a salt for its cache based on the various packages that are
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used when compiling the test files.
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`package-hash` can generate an appropriate hash based on the package location
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(on disk) and the `package.json` file. This hash is salted with a hash
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for the `package-hash` itself.
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`package-hash` can detect when the package-to-be-hashed is a Git repository. In
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the AVA example this is useful when you're debugging one of the packages used to
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compile the test files. You can clone it locally and use `npm link` so AVA can
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find the clone. The hash will include the HEAD (`.git/HEAD`) and its
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corresponding ref (e.g. `.git/refs/heads/master`), any packed refs
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(`.git/packed-refs`), as well as the diff (`git diff`) for any non-committed
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changes. This makes it really easy to test your changes without having to
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explicitly clear the cache in the parent project.
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## Installation
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```console
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$ npm install --save package-hash
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```
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## Usage
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```js
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const sync = require('package-hash').sync
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const hash = sync(require.resolve('babel-core/package.json'))
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```
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`sync()` can be called with a directory or file path. File paths are translated
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to directories using
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[`path.dirname()`](https://nodejs.org/api/path.html#path_path_dirname_p). The
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path must exist. A `package.json` must exist within the directory.
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To get the path to an npm package it's best to use
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`require.resolve('the-name/package.json')`, since `require.resolve('the-name')`
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may resolve to a subdirectory of the package.
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You can provide multiple paths:
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```js
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const hash = sync([
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require.resolve('babel-core/package.json'),
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require.resolve('babel-preset-es2015/package.json')
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])
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```
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An optional salt value can also be provided:
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```js
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const hash = sync(require.resolve('babel-core/package.json'), 'salt value')
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```
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Currently only a synchronous interface is available.
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## API
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### `sync(paths, salt?)`
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`paths: string | string[]` ➜ can be a single directory or file path, or an array of paths.
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`salt: Array | Buffer | Object | string` ➜ optional. If an `Array` or `Object` (not `null`) it is first converted to a JSON string.
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## Compatibility
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`package-hash` has been tested with Node 0.10 and above, including Windows
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support. Note that `git diff` support is not available in Node 0.10.
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